For liquid analyzers to function, a patient sample needs to be removed, such as by aspiration, from a container. Most preferably, such containers are introduced into an analyzer in a stoppered condition, to protect the sample and the apparatus. Such stoppers then must be removed.
Container-opening devices are well-known in the prior art. Such devices will pull a cork out, as described in EPO Publication No. 264,456; flip up a flip-top cap, as described in Japanese Kokai 64/6759; or pull out a plug, as described in Japanese Kokai 62/6171. In all of these, however, the assumption is made that each container presented in the apparatus has in fact the anticipated cover, presented in the anticipated manner. Unfortunately, that is not always the case. Particularly the absence of a cork cover is unfortunate in the case of a device constructed as in EPO Publication 264,456, since the cork-penetrating prongs are likely to wreak havoc on any metal cover used in place of cork or rubber, or even break the container if an unstoppered container projects up into the path of the prongs.
Although it might be assumed that in the absence of the expected cover, most opening devices will simply proceed harmlessly through their opening motions for a container that has no cover to open, this may not always be the case. With some containers, at least, it is desirable to pour a small fraction of the body liquid into a micro-sample cup that is inserted into the larger container. This cup sits at the top of the container exactly where a cover would be. Most conventional cap-or cover-opening devices would seize or otherwise remove such a cup, thereby not only removing the sample liquid from testing but also dumping its contents into the apparatus.
Therefore, prior to this invention there has been no apparatus or means for automatically detecting whether a stopper is present for removal by stopper-removing means, as compared to no stopper at all or some other device at the top of the liquid-containing tube or container.